Field of the Invention
The present invention relates to an electrode material for a lithium-ion rechargeable battery and a method for manufacturing the same.
Description of Related Art
LiFexMn1-x-yMyPO4 which is an olivine-based electrode active material has insufficient electron conductivity. Therefore, in a lithium-ion rechargeable battery in which a phosphate-based electrode active material is used as a cathode active material, a variety of efforts are made for miniaturization of electrode active material particles, conjugation of an electrode active material and a conductive substance, and the like in order to charge and discharge a large amount of electric current (for example, refer to Patent Document 1).
However, the olivine-based electrode active material has a problem of low electron conductivity and low diffusivity of lithium. In addition, in a case in which the primary particle diameter of the olivine-based electrode active material is set to be equal to that of an oxide cathode (several micrometers), a high output which is required for electric vehicle use cannot be obtained. In order to reduce electron conductivity and the diffusion distance of lithium, studies are underway to miniaturize the primary particles of the olivine-based electrode active material. However, in order to obtain a high output, it is necessary to miniaturize the primary particle diameter of the olivine-based electrode active material to several hundred nanometers.
In the olivine-based electrode active material, in a case in which the primary particle diameter is miniaturized to several nanometers, the number of pores between primary particles is increased, and thus an electrode material having a sufficient powder density cannot be obtained. In an electrode produced using this electrode material, electrode material particles do not sufficiently come into contact with each other, and thus the electrode becomes less conductive, and a high output cannot be obtained.
Furthermore, in a case in which the primary particle diameter of the olivine-based electrode active material is miniaturized to several hundred nanometers, it is difficult to control the size of an agglomerate. Here, in a case in which an agglomerate is too small, the fluidity of the agglomerate significantly decreases, and, during the manufacturing of an electrode material, there is a case in which a transfer pipe is clogged. In addition, in order to bring an electrode active material in an electrode and a conductive substance into sufficient contact with each other, a large amount of the conductive substance becomes necessary, which is not preferable. In addition, in a case in which an agglomerate is too large, it is difficult to produce an ordinary electrode for a high-output battery for an electric vehicle which has a thickness of several tens of micrometers.